All women shortlists are patronising to women and unfair to men, particularly those who have spent years knocking doors or climbing the rungs of local politics only to be told they are ineligible to fight a seat in their own backyard.

That’s certainly the view of Edwina Currie, a former Conservative minister.

She tells me: “In principle, people who have suffered discrimination shouldn’t practice it. And in practise, women who’ve come through this route have skipped several steps so their skills may be deficient. Often they’re women who’ve come through various women’s organisations, and they’re a bit…well, limp. It may help to explain why so few of Blair’s Babes made any mark in the House of Commons.”

Edwina Currie

Increasingly in Westminster, though, they are being seen as the only reliable way of ensuring parliament reflects the population it is built to serve.

Jack Straw, first elected in 1979, said: “When I first entered Parliament, there were 19 women MPs in total, from all parties. The signs above the lavatories said ‘Members Only’ – there weren’t even women’s toilets.

“If you’re happy with only seeing half the population represented, that’s alright – otherwise all women shortlists are essential.”

This is a party instinctively opposed to such meddling, but senior sources have confirmed the introduction of all women shortlists is almost certain ahead of the 2020 election.

Only seven out of the party’s 57 MPs are women and it is no exaggeration to say that number could be reduced to 0 after 2015.

The majorities of all the female Lib Dems combined (17,224 votes) is only slightly larger than Nick Clegg's in Sheffield Hallam.

'Blair's babes'...

The former Lib Dem leader Paddy Ashdown summed up the problem when he told activists at a conference fringe: "I don't like women shortlists or shortlists for anybody. I find them illiberal and I find them demeaning to those who are put in that position, and I find them potentially insulting.”

As the room started to applaud, he added: “If this is the only way, through a temporary mechanism, to crack this nut that we have singularly and shamefully failed to crack, then I'll be in favour of it."

The Conservatives have flirted with the idea of the shortlists, but due to resistance in the party, the Prime Minister has tried other methods first.

David Cameron’s priority a-list, introduced in 2005, has helped increase the number of female candidates in winnable seats and the Conservative Women’s Organisation aims to find, mentor and train women to stand for election.

But the statistics speak for themselves

In the 2005 general election, for example two thirds of the new Labour MPs were women, and 23 of 26 came from all women shortlists.

Fast forward five years, and the 2010 vote was hailed as a success for the number of talented women entering Westminster.

But if you drill down into the numbers, only 22 per cent of newly-elected Conservative MPs were women at an election where the party gained nearly 100 seats.

It’s barely surprising that the number of women in cabinet posts has dropped from 35 per cent in 2006 to 17.4 per cent in 2010/11 according to the Equality and Human Rights Commission.

This matters.

It was Margaret Thatcher – someone who would never have called herself a feminist – who said of her election in 1979: “The women of this country have never had a prime minister who knew the things they know. And the things we know are very different from what men know.”

Having a range of voices and experiences around the Cabinet table is crucial in any democracy.

So why is it that women are failing to win parliamentary selections without the distinctly uneven playing field of all women shortlists?

Firstly, local party selection panels are hardly known for being bastions of feminism.

Liz Truss

Liz Truss – now a high-flyer Tory climbing the junior ministerial ranks – nearly fell at the first hurdle thanks to a group being dubbed the “Turnip Taliban”.

Her local party in Norfolk tried to dismiss her as a candidate for the 2010 election after learning of an affair. If the same stringent rules applied to men, imagine how quickly the House of Commons chamber would empty out.

But women must take some of the blame too.

Not enough women put themselves forward to be MPs – whether due to family commitments, a reluctance to spend their weekends at church fetes and school fairs, or simply a lack of interest in politics.

But while the reasons behind the lack of women in Westminster are complex, the solution is simple – even if unpalatable.

It’s easy to say that increasing female representation in parliament is important.

The difficult bit is taking the uncomfortable steps necessary to sort it out.

Sophy Ridge is Political Correspondent for Sky News. Since joining Sky News, Sophy has covered stories from the US elections to the arrival of a cat at Downing Street. She has gained recognition for her round-the-clock broadcasting at the annual party conferences and during the closure of the News of the World - ironically the place where she began her media career.